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ENTERPRISE INFORMATION SYSTEMS VI
4 MEASURING DESIRABILITY
AND MODIFIABILITY OF
GOALS
Besides the classification of goals as core and
peripheral, the attributes desirability (level of
importance for a goal to be met), and modifiability
(level in which a goal can be modified) are proposed
as attributes for goal description when selecting
COTS components (Alves and Filkenstein, 2002).
By using an AGORA graph, we can estimate the
quality of several properties of the adopted goals.
Particularly, correctness is assumed as a quality
factor that represents how many goals in a
specification meet stakeholder’s needs. Correctness
in AGORA is strongly related to contribution values
on the path of the adopted goal as well as on its
stakeholder’s preference value. Particularly, the
average stakeholder’s preference value of the
adopted final goals (Cup) is defined by Kaiya et al.
(2002) as:
Cup = AVE (� f �FinalGoal, s � Stakeholder, m � Preference
{ms,customer | has(f,m)})
where ms,customer means a stakeholder’s
preference value evaluated by the stakeholder s in
the preference matrix m. The results of the
calculation for all the core goals of Figure 2 are as
follows:
Cup(RA) = ((8 + 8 + 5) + (-2 + 0 + 0) + (-3 + 0 +
0)) / (3 + 3 + 3) / 10 = 0.18
Cup(CE) = ((7 + 10 + 10) + (10 +10 + 10) + (7 +
10 + 10)) / (3 + 3 + 3) / 10 = 0.93
Cup(BC) = ((0 – 3 – 5 ) + (0 – 5 – 8 ) + (0 – 3 –
5)) / (3 + 3 + 3) / 10 = – 0.32
Cup = (0.18 + 0.93 – 0.32) / 3 = 0.26
In COTS component selection, this measure
might indicate the degree of agreement on
stakeholder’s preferences, i.e. on the desirability of
the core goals of the abstract specification SC.
Lower results of Cup, such as 26% in our case, show
a need of further discussion on the required
functionality of the component C; i.e. causes of
disagreement should be detected. For example,
stakeholders have different goals, even their
perceptions of reality vary significantly. Then,
scenarios may drive the agreement process and
establish partial consistency among existing systems
– all systems involved in using the COTS
component.
On the other hand, modifiability is about the
degree in which committed goals can be changed
when selecting COTS components. Let’s briefly
clarify the point: suppose there is a strong agreement
on a set of goals (Cup = 80%), however the search
of COTS candidates offering the functionalities
shows that there are no candidates available. In this
case, evaluators should have agreed on the degree in
which the goals (even categorised as core) can be
modified. Then, the modifiability of the goals will
help to decide on acquiring COTS components with
less functionality than required, adding the
functionality by means of an adapter (such as a
wrapper), or building the missed functionality from
scratch.
In (Kaiya et al., 2002), the quality metrics for
modifiability include how an AND-OR graph is
closed to a tree structure. When there are many
incoming edges to a goal, the goal contributes to an
achievement of many goals. In consequence, these
many goals should be under consideration in case of
changing the goal. The quality metric is defined as
follows:
Tre = #{g � RefinedGoals | #{e|incoming(g,e)=1}}
#RefinedGoals
RefinedGoals = Goals – Initial Goals
Calculations for Figure 2 show that there are 3
initial goals and 13 refined goals, from which only 9
have one incoming edge. Then, the result of the
calculation of Tre (modifiability) for Figure 2 is 9 /
13 = 0.69. In other words, the figure shows four
goals whose incoming edges are more than one (13 –
4 = 9), out of 13 refined goals.
We should note that other quality metrics such as
unambiguity, completeness, and consistency might
be calculated on AGORA graphs. However,
desirability and modifiability are the main properties
when we apply the analysis on abstract
specifications of COTS components aiming at being
included into a selection procedure.
4.1 Weighting the Functional
Requirements of Sc
Functional mappings of SC, as introduced in section
2, are associated to one or more refined goals of the
graph. By doing so, an agreement among
stakeholders might be achieved by calculating the
desirability of each group of refined goals
representing a particular mapping. For the example
in Figure 2, calculations should be split into three
groups: one containing the core goals referring to the